Problem with manuals - Setting up an AP in the field


Joe Zeglinski
 

Hi,

Although I have had a bit of practice with setting up my AP-900, in the yard, I decided to reread the manuals, again.

Two things bothered me a bit, and perhaps I am overlooking something there - which is possible, since the manuals haven't changed, in this regard, in maybe a decade.

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(A):
In the AP Mount assembly manual, under "Assemble Pier":

"Slide the three legs onto the nubs of the base and rotate the assembly so that one of the legs
points toward north (or south, if that is your preference)."

For those in northern latitudes, perhaps, if you "prefer to point one pier leg south", then the counterweights will hang down (during OTA installation), between the other two pier legs. This is a somewhat less stable position, than if the weights hung over a pier leg pointing north. If you accidentally push the assembled system, the moment arm is somewhat shorter between legs, than if it were over them, and the whole thing could topple over. This is worsened if the portable pier is set up on uneven ground, or the feet dig into soft soil.

The other argument against this "south facing preference" is that if you are using an AP portable pier, aligning on the pole with the polar scope, means that the turn buckle and rod would be right against your cheek (or worse, between your legs), or you have squat to the side. At latitudes above 45N, the PAS eyepiece may be unreachable. In the more stable northward position, you can position yourself more comfortably between the two southern pier legs, to use the PASILLx alignment scope. Straddling the steel turn buckle rod (or any metal tripod leg), on a cold winter night to do the polar alignment, can be a chillingly uncomfortable experience.

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(B):
GTO KEYPAD Manual: under "N Polar Calibrate - Calibrating with Polaris" (pg 18)

STEP #2 says that noting the Z-value (LST) in the upper corner of the display, you can "use a star atlas" to push (or slew) your OTA to the reference star position.

Seems to me that the setting circles aren't mentioned enough, almost as though they are there as a fashion statement of old. The procedure as stated in the manual, requires some expertise in recognizing calibration stars, or at least finding them with some difficulty, in the washed out suburban skies, or to pick one out, in a shower of stars at a dark site. That is even more difficult for those of us from the city, who rarely get to dark sites. The task is that much harder, if the calibration star may not be ideally placed, perhaps dodging some tree branches, or is about to emerge from some obstruction. The modified procedure should solve these problems.

I would change step #2 in the manual to:

Step "2a"
After roughly aligning your mount on the pole, (using your PAS, etc.), with your OTA still in the ubiquitous GEM ... "CWD stance" - "Park #3 Position" - note your LST from the keypad's displayed Z-value, ADJUST your DEC circle to 90N (or, if you are confident, 89N ), and your RA circle to that Z-Value.

Step "2b"
Select a specific calibration star from the list in the display, make a note of its RA &DEC, and only now, push your OTA - to that analog setting circles position.
Then ... Do the "NEWS" ... (i.e. centre the star with the N-E-W-S slew buttons), and if required, with the alignment star centred, refine the adjustment of the circles even more precisely at the listed calibration star coordinates .

Steps #3 and #4 in the manual can be deleted, with their information incorporated in the "STEP 2a and 2b" above.
The adjustment of the setting circles could be rechecked, if you choose to repeat the alignment cycle steps on the same, or a different star. However, that will probably not be necessary.

This minor change in procedural wording, would likely make the star atlas largely unnecessary.

The same amendment could also be applied to the 2-Star Calibration.

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Perhaps I have misunderstood the manual, and welcome any rebuttal.
I think we can make more use of the Z-Value in the display, and of the analog setting circles.

Thanks,
Joe

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